Relation between reactivity and electronic structure for α′_L-, β- And γ-dicalcium silicate: A first-principles study

The effect of the electronic structures of α′_L-, β-, and γ-dicalcium silicate (α′_L-, β- and γ-C₂S, C = CaO, S = SiO₂) on hydration reactivity have been investigated by first-principles calculations. Active O atoms with larger charge densities are found in α′_L- and β-C₂S, while they are absent in γ-C₂S. The local density of states of valence band maximum in α′_L- and β-C₂S is highly localized around active O atoms, whereas that in γ-C₂S is homogeneously dispersed. For the active O-2p orbital in α′_L- and β-C₂S, the highest orbital energy in the partial density of states is about 0.31 eV higher than that of the inactive O in γ-C₂S. These differences make the active O atoms of α′_L- and β-C₂S more susceptible to electrophilic attack and result in higher hydration reactivity for α′_L- and β-C₂S.